Seal for closing caps of containers, in particular bottles, closing cap and means for making the seal

Abstract

NOT VISIBLE DUE TO STATUS OF PATENT

Description

[0001] DESCRIPTION

[0002] SEAL FOR CLOSING CAPS OF CONTAINERS, IN PARTICULAR BOTTLES, CLOSING CAP AND MEANS FOR MAKING THE SEAL.

[0003] Technical field

[0004] This invention relates to a seal for closing bottles and, in particular, relates to a seal mounted in the cap, generally, but without limiting the scope of the invention, made of metal, for sealing the opening of a bottle (or, more generally, a container).

[0005] Background art

[0006] As is known, caps of different types, with screws, of the crown type or also with pull-off opening, and other similar types are usually used for closing bottles or other similar containers, generally made of glass, provided for packaging liquid products, intended for food use, such as beverages, medicines, supplements, kitchen products, etc., or also for purposes which are more general and different from food supply.

[0007] More specifically, the invention relates in effect to the seals which are applied between the caps and the openings of the bottles or other similar containers, seals which are prepared for adhesion on the flat inner surface of the caps before their application on the bottles.

[0008] Although this invention is suitable for use for caps intended for application on bottles and similar containers (jars, vials, etc.), for the sake of convenience and brevity only bottles will be referred to below, that is to say, including all the above-mentioned containers and in no way limiting the scope of the invention.

[0009] Currently, the caps, for example those made of metal, consist of a laminated piece with a flat circular part with an inner face and an outer face, from the edge of which extends a peripheral annular part, intended to be fitted and fixed in different ways, according to the type of cap, on the opening of the bottle, and a seal fixed to the inner face of the flat circular part of the cap.

[0010] When the metallic cap is positioned on the opening of the glass bottle, the descending annular part is subjected to a plastic forming process, in such a way as to adhere to the outer profile of the opening of the bottle, copying the outer thread of the opening of the glass bottle, for the screw cap, or the more regular curvilinear shape for the crown cap or the one with the pull-off opening.

[0011] This allows a coupling between the sealing surface of the opening of the glass bottle and the seal. In particular, the outermost annular zone of the seal comes into contact on the sealing surface of the opening of the glass bottle.

[0012] So that the seals can correctly seal the bottled liquids, even those under pressure such as fizzy water and drinks, beer and other similar beverages, the material and the thickness of these seals must be such as to be compressed at the moment of applying the cap on the bottle, and then tend to re-expand after the application, in this way achieving the seal of the closure.

[0013] This effect assumes importance, in particular, for the crown type caps, for which the clamping on the bottle is ensured by the clamped edges which attach to the opening of the bottle and keep the seal firmly pressed above said opening.

[0014] The materials normally used for the seal are therefore flexible plastic materials, such as polyethylene, polypropylene, elastomeric copolymers, ethylene vinyl acetate, polyethylene-polypropylene alloys, and other similar materials.

[0015] In order to optimise the seal, however, which could be partly compromised by the slight release of the clamped edge, due to the elastic return of the material after the folding on the opening of the bottle of the crown cap, but in general also for all types of caps, the prior art teaches the provision of a pair of lips which extend from the seal towards the open base of the cap to which they are applied. One of the two lips, which extends along the outer perimeter of the seal, is intended to rest on the upper outer part of the opening of the bottle, at the bevel or rounding generally made to avoid a sharp edge.

[0016] The other lip extends towards the open base of the cap, but along a circumference of the seal which is more inside, in such a way as to be inserted with slight interference, in the hole of the opening of the bottle, when the cap is applied to it.

[0017] The seals of known types have some features which can undergo various improvements.

[0018] For example, the provision of the two lips involves significant consumption of material, considering the limited thickness of the flat central part with respect to that of the lips, which also extend for the entire respective circumference.

[0019] Another feature which can be improved is the geometrical shape of the seal, which is complex with two lips, requiring equally complex equipment or production processes.

[0020] In general, the geometrical shape of the seal, in practice the profile of the axial cross-section of the seal, can be optimised to reduce the complexity and possibly improve the sealing performance.

[0021] Moreover, the complexity of the shape facilitates the occurrence of production defects, causing a greater number of rejects of the finished seals.

[0022] Another problem is the presence of the outermost lip which can cause damage to the seal during application of the cap on the bottle, in particular for the crown caps, due to the possible stretching of this outermost part determined by the folding of the corresponding zone of the cap at the moment of seaming on the opening of the bottle.

[0023] Disclosure of the invention

[0024] The aim of this invention is to provide a seal for a cap for bottles which does not have the above-mentioned problems with respect to the prior art seals, in particular which has a simpler cross-section profile in such a way as to make their production equally simpler and more economical, contributing to saving of material, but improving the sealing characteristics. Another aim of this invention is to provide a tool designed to produce the seal as proposed on the basis of the above-mentioned aims, such as to contribute to obtaining the above-mentioned aims.

[0025] Another aim of the invention is to provide a cap-seal assembly which incorporates the features such as to obtain or contribute to achieving the above-mentioned aims.

[0026] These and other aims, which will become clearer from the following description, are all obtained by a seal formed and sized as described in claim 1 .

[0027] The means that for producing the seal according to the invention, as described in claim 13 and the assembly consisting of a cap and the relative seal, as described in claim 11 , also contribute to achieving the above-mentioned aims, and others which will become evident to experts in the sector.

[0028] The structural and functional features of the invention, in order to achieve the above-mentioned aims, are described in the independent claims mentioned above and described below, whilst the dependent claims describe further features and variations of the respective embodiments.

[0029] Brief description of drawings

[0030] These structural and functional features and variations, as well as the advantages obtained from the present invention, are more apparent from the detailed description which follows, with reference to the accompanying drawings which illustrate preferred, non-limiting example embodiments of it, and in which:

[0031] - Figures 1A-1 E show different views, some in cross section, of the seal obtained thanks to the adoption of this invention;

[0032] - Figures 2A-2D illustrate the assembly made up of the cap and the seal obtained thanks to the adoption of this invention, according to different embodiments, ready to be applied to a bottle;

[0033] Figures 3A and 3B illustrate a punch which constitutes the main part of the means for producing the seal according to this invention, seen in cross-section to highlight the mutual positioning of its components;

[0034] Figures 4A and 4B illustrate the same punch broken down into its main components;

[0035] Figures 5A and 5B are perspective views of the punch, broken down into its main components in an exploded configuration;

[0036] Figures 6A and 6B are perspective views of the assembled punch;

[0037] Figure 7 illustrates a detail in cross-section of the seal; and

[0038] Figure 8 illustrates a detail in cross section of the punch for producing the seal;

[0039] Figures 9A and 9B show the results of a first experimental text performed with the seal according to the preceding drawings;

[0040] Figures 10A and 10B show the results of a second experimental test performed with the seal according to Figures 1 to 8.

[0041] Detailed description of preferred embodiments of the invention

[0042] Figures 1 to 8 describes a seal 1 mounted in a cap 14 generally, but not necessarily, made of metal, used for sealing the opening of containers 12, in particular containers made of glass (but not necessarily), for example, but not exclusively, bottles.

[0043] It should be noted that, as already mentioned in the introduction, the container may consist, for example, of a bottle 12, as shown in particular in Figure 2A, in which a portion of the opening 13 is illustrated of the bottle, as the type of container is not decisive for the purposes of understanding of the invention.

[0044] Therefore, any container, such as jars, vials, etc. may be the subject of application of this invention, provided that they have suitable features in particular with respect to the opening. As already mentioned, for the sake of convenience and brevity, only bottles will be mentioned below, that is to say, including all the above- mentioned containers and in no way limiting the scope of the invention.

[0045] The seal 1 illustrated in Figures 1A to 1 E is provided for sealing caps 14, as illustrated in Figures 2A and 2B intended for closing containers, in particular bottles.

[0046] The caps 14 may be of any type, but in this case reference will preferably be made to caps of the crown type 14C (Figure 2C) or of the type with pull- off openings 14B (Figure 2B) or 14C (Figure 2D) or more generically metallic caps 14A (Figure 2A).

[0047] These caps 14 comprise a flat circular part 15 from the edge of which extends a peripheral annular part 16 intended to be fitted and fixed on the opening 13 of a bottle 12.

[0048] The shape consisting of the flat circular part 15 and the peripheral annular part 16 of the cap defines in this way an inner face 18 and an outer face for the flat circular part 15 of the cap 14.

[0049] The seal 1 is intended to be positioned between the upper part of the opening 13 of a bottle 12 and the relative cap 14, in such a way as to guarantee the seal of the bottle 12, in particular when it contains aerated liquids.

[0050] Precisely to give greater sealing properties, the seal 1 is made of materials which are more suitable for this purpose, such as, for example, a polymer, PVC, polyethylene, polypropylene, elastomeric copolymers, ethylene vinyl acetate, polyethylene-polypropylene alloys, and others which are similar.

[0051] Structurally, the seal 1 comprises a central deformable sealing disc 2, with an adhesion side A, intended to adhere to the inner face 18 of the flat circular part 15 of the cap 14, and a supporting side B which, on the other hand, rests on the opening 13 of the bottle 12, when the cap is applied on it.

[0052] According to the invention, and with reference also to Figure 7, the seal also comprises a single circular lip 4, which is positioned on the supporting side B of the deformable sealing disc 2, in such a way as to be extended towards the open base 17 of the cap 14, when the seal 1 is inserted inside the latter (Figures 2A and 2B).

[0053] It should be noted that the lip 4 has an inclined outer side 5 (that is to say, facing towards the outer perimeter of the seal), in such a way as to rest on the inner edge 11 of the opening 13 of the bottle 12 when the cap 14 is applied on it.

[0054] Again according to the invention, the lip 4 has a triangular cross-section (Figure 7), with the inclined side 5 made according to an angle of between 10° and 80° (even more preferably between 30° and 60°) whilst, preferably, the side 6 opposite the inclined side 5 is substantially at right angles with respect to the deformable sealing disc 2.

[0055] This allows the gases present inside the bottle to apply a pressure on the lip 4 towards the edge 11 of the opening of the bottle 13, improving the seal of the cap.

[0056] In short, experimental studies performed by the applicant have shown how this profile makes it possible to obtain optimum performance of the bottle, whilst at the same time allowing an optimisation of the materials.

[0057] In order to obtain the best performance of the seal, the side joined to the deformable sealing disc 2 may have an extension H of between 0.3 to 2 mm, still more preferably from 0.7 to 1.5 mm, more preferably from 0.8 to 1 .2 mm.

[0058] Preferably, the lip 4 with a triangular cross-section has the side joined to the deformable sealing disc 2 of extension H between 0.5 to 1.5, more preferably equal to 1 .00 mm and the inclined side 5 oriented according to an angle of between 35° and 55°, preferably 45°.

[0059] These dimensions have been shown to give the best sealing characteristics to the cap 14.

[0060] In order to further optimise the sealing features, the peripheral edge 3, outside the lip 4, has a thickness (M, X) greater than the thickness P of the part of the deformable sealing disc 2 which is more inside with respect to the lip 4.

[0061] More specifically, the peripheral edge 3 of the deformable sealing disc 2, outside with respect to the lip 4 and intended to rest on the upper edge of the opening 13 of the bottle 12, has a thickness of between 0.3 and 2 mm, even more preferably between 0.85 mm and 1 .05 mm.

[0062] Preferably, the peripheral edge 3 of the deformable sealing disc 2 has a concave shape, so that the minimum thickness M, at the bottom point of the concave shape, is 0.85 mm whilst the maximum thickness X of the peripheral edge 3 reaches the thickness of 1 .05 mm.

[0063] This feature is more apparent in Figure 7, which shows a scaled-up detail of the seal 1 .

[0064] An important feature of the seal 1 made according to the invention is that the deformable sealing disc 2 has a diameter D less than the diameter T of the flat circular part 15 of the cap 14.

[0065] The reduction of the diameter D must be such as to bring the perimeter of the deformable sealing disc 2 to be positioned before the curved stretch 19 which joins the flat circular part 15 to the peripheral annular part 16 intended to be fitted and fixed on the opening 13 of the bottle 12 (Figures 2A and 2B).

[0066] It should be noted that this feature assumes important importance for the achievement of the aims mentioned in the introduction, as it prevents the marginal part of the seal 1 from remaining involved in the folding of the peripheral annular part 16 when it is fixed on the opening 13 of a bottle 12. This avoids stretching or even tearing of the deformable sealing disc 2, which would, on the other hand, be possible if the marginal part of the seal 1 were pulled towards the outside and downwards when the cap 14 is seemed on the opening of the bottle 13.

[0067] As already mentioned, Figures 2A and 2B illustrate an assembly comprising a cap 14 for closing containers, in particular bottles, consisting of a flat circular part 15 with a peripheral annular part 16 which is fitted and fixed on the opening 13 of a bottle 12, and a relative seal 1 , applied inside the cap 14.

[0068] For producing the seal 1 use is made of production means comprising a punch 20, designed to perform, according to known methods, the moulding of a thermoplastic material for obtaining the seal 1 .

[0069] The punch 20 has an impression on its lower head such as to make the seal 1 as described above.

[0070] In more detail, the punch 20 comprises a central rod 21 , for supporting the tool, with a lower end stretch 22 separated from the remaining body by a drain, that is to say, a groove 23 with a diameter greater than the latter.

[0071] The circular lower surface 24 of the lower end stretch 22 is flat and preferably treated with mirror polishing.

[0072] Around the lower end stretch 22 there is an intermediate ring 25 positioned in such a way that the flat circular lower surface 24 of the end stretch 22 of the rod 21 remains protruding with respect to the corresponding retracted end 26 of the intermediate ring 25.

[0073] In order to achieve this mutual positioning, the intermediate ring 25 has the inner surface 30 stepped in steps, so that the shoulder 34, which is formed in that way, makes contact with the corresponding shoulder created by the lower end stretch 22 with a diameter larger than the remaining body of the rod 21 .

[0074] Moreover, the inner edge 27 of the retracted end 26 of the intermediate ring 25 is bevelled according to an angle corresponding to the inclination of the inclined side 5 facing towards the outside of the seal 1 .

[0075] Advantageously, the angle is inclined by 45°, as that inclination value is the one which has proved the best to obtain the sealing of the seal 1 inserted between the cap 14 and the opening 13 of the bottle 12.

[0076] The outer surface 31 of the intermediate ring is also stepped in steps in such a way as to create corresponding shoulders 35, against which corresponding shoulders of an outer containment ring 28, fitted on the intermediate ring 25, abut.

[0077] It should be noted that with the placing alongside each other of the corresponding shoulders 35, the end 29 of the containment ring 25 remains protruding with respect to the flat circular lower surface 24 of the end stretch 22 of the rod 21 to a extent greater than the thickness P of the deformable sealing disc 2 of the seal 1 (Figure 8) and even more with respect to the retracted end 26 of the intermediate ring 25, to the extent corresponding to the thickness (M, X) of the peripheral edge 3 of the deformable sealing disc 2 of the seal 1 .

[0078] The inside diameter of the containment ring 28 is greater than the diameter of the end stretch 22 of the stem 21 , to an extent so as to define the total width C of the peripheral edge 3 and of the lip 4 (again Figure 8).

[0079] It should be noted that this spatial configuration of the three elements which constitute the punch 20 allows the lip 3 to be shaped with the proportions and the shape as described above.

[0080] The drain grooves 32 are made at the transition points between one step and the other of the inner surface 30, 33 and outer surface 31 of the intermediate ring 25 and of the containment ring 28, respectively.

[0081] In short, once the seal 1 has been made by moulding with the use of the punch 20, according to known methods, it is applied with the adhesive side A adhering to the inner face 18 of the flat circular part 15 of the cap 14, in such a way that the supporting side B remains facing towards the open base 17 of the cap.

[0082] The cap 14 - seal 1 assembly is then applied, using automatic handling and application systems, on the opening 13 of a bottle 12 filled with a liquid product.

[0083] The seeming of the cap 14 is performed with a process for plastic deformation of the peripheral annular part 16 of the cap 14 which is fitted and remains in this way fixed on the opening 13 of the bottle 12.

[0084] During this operation, the peripheral marginal part of the seal 1 is not subjected to stresses, so that no other part of the seal undergoes stretching, tearing or damage in general.

[0085] The elasticity of the material, with which the seal is produced, then guarantees the sealing even when the peripheral annular part 16 fixed on the opening 13 of the bottle 12 performs a slight return movement due to the elasticity of the metallic material.

[0086] The use of the seal obtained according to the invention allows an easy and convenient production of the cap with improvement of the sealing characteristics and a considerable saving of material.

[0087] Advantageously, the use of the production means described here makes it possible to obtain the seal easily without particular problems due to the (non) complexity of its shape.

[0088] Figures 9A, 9B, 10A, 10B show the results of some tests performed with the seal 1 according to the invention.

[0089] A plurality of seals were applied to crown type caps.

[0090] The caps were then used in the tests described below, and the caps thus obtained were then applied on a batch of bottles comprising bottles of a same type, which was the subject of a first and a second experimental test, aimed at checking the performance, with regard to the sealing, of the seal 1 according to the invention.

[0091] The first experimental test, which is the subject of the diagram in Figure 9A, (the so-called “secure seal test”) comprises blowing pressurised air inside the capped bottles, using a piercing nozzle inserted in the cap, to check the seal.

[0092] The test is performed as follows:

[0093] 1 - capping of all bottles;

[0094] 2- pasteurization of all the bottles;

[0095] 3- waiting for a predetermined time (24h);

[0096] 4- subjecting the bottles to 7.0 bar, waiting for a predetermined time (1 minute) and subsequently increasing the pressure of the bottles to 10 bar. Figure 9B shows that on average the bottles tested withstood a pressure of 9.5 bar, with a minimum of 8.5 bar and a maximum of 10 bar (and standard deviation of 0.56 bar). These numerical results, relating to the batches subjected to the test, are summarised in Figure 9B. These performance levels are excellent, that is to say, completely acceptable, which highlight how all the capped bottles have withstood at least up to a pressure of 7 bar and there are therefore no rejects.

[0097] Figure 10A shows, on the other hand, a second experimental test, the so- called “IMPACT TEST”.

[0098] The procedure implemented in this second so-called “IMPACT TEST” is as follows:

[0099] 1- capping of all bottles;

[0100] 2- pasteurization of all the bottles;

[0101] 3- waiting for a predetermined time (24h);

[0102] 4- inclining each capped bottle at 45° and striking, with a single impact, each capped bottle by means of a calibrated weight of 35g which falls from a height of 0.5m (the impact occurs substantially on the area 19 of Figure 2A);

[0103] 5- waiting for a predetermined time (24h);

[0104] 6- performing the SST (“secure seal test”) described above with reference to Figures 9A and 9B.

[0105] Figure 10A shows the results of the “secure seal test” obtained according to the procedure described above.

[0106] Also in this case, as shown in Figure 10B which summarises the overall results, the average of the maximum pressure to which the cap withstood is 9.6 bar, whilst the minimum pressure to which the cap withstood has never fallen, in any sample, below 7 bar (and therefore no bottle would have been rejected).

[0107] In this case, too, the performance levels are absolutely remarkable.

[0108] The above shows, experimentally, that the seal 1 is able to obtain excellent performance levels, with regard to the pressure to which the cap is able to withstand, with considerable savings in terms of material and costs of the seal.

[0109] The Applicant has also observed that in the bottle samples subjected to the impact test there were no signs of chipping of the bottle or denting of the cap, unlike what has been observed in the majority of prior art seals I closing capsules. This aspect should not be overlooked, since it should be noted that the seal 1 has been able, in particular in the impact test, to dampen the blow deriving from the impact with the “sample” mass, preventing the cap or the bottle from being ruined.

Claims

CLAIMS1. A seal (1 ) for sealing caps (14) for closing containers (12), in particular bottles, with said caps (14) each consisting of a flat circular part (15), from the edge of which extends a peripheral annular part (16) intended to be fitted and fixed on the opening (13) of a container (12), and defining an inner face (18) and an outer face, said seal (1 ) being intended to be applied to the cap (14) so as to be positioned between the upper part of the opening (13) of a container (12) and the relative cap (14), and comprising a central deformable sealing disc (2), with an adhesion side(A), intended to adhere to the inner face (18) of said flat circular part (15) of the above-mentioned cap (14), and also comprising a supporting side(B), intended to rest on the opening (13) of the bottle (12) and a peripheral edge (3); said seal (1 ) being characterised in that it also comprises a single circular lip (4) positioned on said supporting side (B) of said deformable sealing disc (2) in such a way as to be extended towards the open base (17) of said cap (14), when said seal (1 ) is inserted in the latter, and in that said lip (4) has an inclined outer side (5), such that it rests on the inner edge (11 ) of said opening (13) of the container (12) when the cap (14) is applied on it, and with the peripheral edge (3) of said deformable sealing disc (2), outside the above-mentioned lip (4), having a thickness (M, X) greater than the thickness (P) of the part of the deformable sealing disc (2) more inside than the above-mentioned lip (4).

2. The seal (1 ) according to claim 1 , wherein said lip (4) has a triangular cross-section, with the side joined to said deformable sealing disc (2) having an extension (H) of between 0.3 and 2 mm.

3. The seal (1 ) according to claim 1 or 2, wherein said inclined side (5) is inclined according to an angle of between 10° and 80° and with the side (6) opposite said inclined side (5) substantially at right angles relative to said deformable sealing disc (2).

4. The seal (1 ) according to any one of the preceding claims and claim 2, wherein said lip (4) with a triangular cross-section has the side joined to said deformable sealing disc (2) with an extension (H) between 0.5 and 1 .5 mm, preferably equal to 1 .00 mm.

5. The seal (1 ) according to any one of the preceding claims, wherein said inclined side (5) is inclined according to an angle of between 35° and 55°, preferably 45°.

6. The seal (1 ) according to one of the preceding claims, wherein said peripheral edge (3), on the outside of said above-mentioned lip (4), is intended, in use, to rest on the upper edge of the opening (13) of the bottle(12).

7. The seal (1 ) according to any one of the preceding claims, wherein said peripheral edge (3) has a thickness of between 0.3 mm and 2 mm.

8. The seal (1 ) according to any one of the preceding claims, wherein said peripheral edge (3), outside the above-mentioned lip (4), has a surface (7) intended to rest on said opening (13) of the container (12) having a concave shape, so that the minimum thickness (M), at the bottom point of the concave shape, is less than 1.5 mm, preferably is 0.85 mm whilst the maximum thickness (X) of said peripheral edge (3) is less than 2 mm, preferably is 1 .05 mm.

9. The seal (1 ) according to any one of the preceding claims, wherein the deformable sealing disc (2) has a diameter (D) less than the diameter (T) of said flat circular part (15) of said cap (14), so as not to correspond to the curved stretch (19) which joins said flat circular part (15) to said peripheral annular part (16) intended to be fitted and fixed on the opening(13) of the bottle (12).

10. The seal (1 ) according to any one of the preceding claims, made with one or more of the following materials: a polymer, PVC, polyethylene, polypropylene, elastomeric copolymers, ethylene vinyl acetate, polyethylene-polypropylene alloys, and other similar materials.

11. An assembly consisting of a cap (14) for closing containers (12), inparticular bottles, consisting of a flat circular part (15) from whose edge extends a peripheral annular part (16) intended to be fitted and fixed on the opening (13) of a container (12), preferably a bottle (12), and defining an inner face (18) and an outer face for said flat circular part (15), and a seal (1 ) for sealing the cap (14) on a container (12), characterised in that it comprises a seal (1 ) made according to any one of the preceding claims.

12. The assembly according to the preceding claim, wherein said cap (14) is constituted by a metallic cap (14) of the crown type (14A) or of the pull-off type (14B).

13. Means for producing a seal (1 ) for sealing closing caps of containers (12), in particular bottles, characterised in that it comprises a punch (20) for moulding a thermoplastic material having on its lower head an impression such as to make a seal (1 ) as defined by one or more of claims 1 to 10.

14. The production means according to claim 13, wherein said punch(20) comprises a central rod (21 ) for supporting the tool having a lower end stretch (22) separated from the remaining body by a drain (23) and with the flat circular lower surface (24), an intermediate ring (25) situated around said lower end stretch (22) with said flat circular lower surface (24) of said rod (21 ) protruding relative to the corresponding retracted end (26) of said intermediate ring (25) and with the inner edge (27) of said retracted end (26) bevelled according to an angle corresponding to the inclination of said inclined side (5) facing towards the outside of said seal (1 ), and with an outer containment ring (28), fitted on said intermediate ring (25) with an end (29) protruding relative to the latter to the extent corresponding to the thickness (M, X) of said peripheral edge (3) of said deformable sealing disc (2) of said seal (1 ) as well as protruding relative to said flat circular lower surface (24) of the rod to the extent corresponding to the thickness (P) of the deformable sealing disc (2) of the seal (1 ), with said containment ring (28) having a diameter greater than said end stretch (22) of said rod(21 ), such as to define the overall width (C) of said peripheral edge (3) andof said lip (4).

15. The production means according to claim 13 or 14, wherein said intermediate ring (25) has the inner surface (30) and outer surface (31 ) stepped in steps with grooves (32) made at the transition points, and wherein said containment ring (28) has the inner surface (33) stepped in steps.